The present invention relates to a storage system, and more particularly to a backup of data among a plurality of storage systems.
A conventional technology of such a storage system is disclosed in JP-A-11-167521. This publication discloses a storage system which has an interface (host adapter, CHA) to a higher level device such as a host computer, an interface (disk adapter, DKA) to a storage in a storage system, a cache memory (CACHE) and a shared memory (SM), which are interconnected by a common path system.
To extend the storage system disclosed in the above publication, there is proposed a technology for interconnecting a plurality of storage systems. Such a configuration is called a clustering storage system. And, the individual storage systems configuring the clustering storage system are called storage system units.
Meanwhile, there is another technology which disposes a separate storage system physically away from a storage system for holding data on the assumption that the storage system may be broken because of a disaster or the like and physically connects them through a telephone line or the like. According to this technology, one storage system holds (backs up) a copy of data which is stored in the other storage system. For example, even if one of the storage systems is broken and its data becomes unusable, the other storage system can be used to quickly resume the use of the data.